In a process of transmitting data in a wireless manner, a network-side device and a user-side device generally follow a hierarchical model for data transmission, that is, an application layer, a transfer control protocol (Transfer Control Protocol, TCP) layer, a network layer, a radio link control (Radio link Control, RLC) layer, a MAC (Media Access Control, Media Access Control) layer, and a physical (Physical, PHY) layer. When the network-side device sends data to the user-side device, the data starts from an application layer of the network-side device, after passing through a transfer control protocol layer, a network layer, a Radio Link Control layer, a media access control layer, and a physical layer of the network-side device, arrives at a physical layer of the user-side device through a transmission link, passes through a Radio Link Control layer and a network layer of the user-side device, and finally, arrives at an application layer of the user-side device; and vice versa.
To avoid a case in which a data loss or a data error occurs in a data transmission process, a receive data acknowledgment mechanism is introduced into the foregoing data transmission process, where an acknowledgment at the TCP layer is to ensure correctness of transmitting a data packet at the TCP layer, and an acknowledgment at the RLC layer is to ensure correctness of receiving a data packet at the RLC layer. In a condition provided with acknowledgments at both the RLC layer and the TCP layer, a data packet transmission procedure is shown in FIG. 1.
Currently, a TCP acknowledgment packet (TCP ACK; ACK: Acknowledgment, acknowledgment) is sent in two manners: piggybacked (that is, sent together with a data packet) and independently sent (that is, data is not included in the TCP acknowledgment packet, and only header information is included). A format of a TCP data packet header is shown in FIG. 2, where a 4-bit (bit) header length indicates a quantity of pieces of 32-bit information that appears in a TCP packet header. A TCP packet header is a maximum of 60 bytes (byte), and is generally 20 bytes.
During one time of data packet transmission, an RLC-AM mode (that is, an RLC acknowledged mode; AM: Acknowledged Mode, acknowledged mode) is used, where both an RLC layer and a TCP layer at a receive end device may send an acknowledgment packet, and receiving of a TCP acknowledgment packet may trigger sending of an RLC acknowledgment packet again. During transmission of a single data packet, particularly, transmission of a single small data packet, one data packet at the foregoing application layer is corresponding to a maximum of three acknowledgment packets on an air interface (Air Interface, air interface, that is, an interface between a mobile terminal and a base station). When an independent TCP acknowledgment packet appears, a data packet is relatively large, which causes a waste of air interface resources, and a large quantity of acknowledgment packets cause interference to other communication data.